I did some research on fugitive ink and they were used as a deterrent to anyone attempting to alter the stamp, when immersed in water the ink fades preventing any removal of fiscal pen cancellations.
But I cannot see any cancellations of any type to support the stamp having fugitive ink deployed, as it looks unused, fugitive ink being deployed would have kept visible remnants of a cancellation remaining on the stamp.
I believe it was a changeling, as the ink faded due to exposure to a strong light or to some natural or not so natural chemical reaction.
As it seems to be unused and there is no gum, the missing gum is mostly due to rust or toning on the gum being removed to save the stamp, I have seen many unused stamps, especially from the Victorian era missing its gum, it's a common sight as a result of this.
Of course on the other hand if the stamp was immersed in water to remove the gum (there is a better way to remove the gum without immersing it in water), it would activate the fugitive ink.